This invention is generally in the field of devices and methods for controlled exposure or release of reservoirs contents.
U.S. Pat. No. 5,797,898, No. 6,527,762, No. 6,491,666, and No. 6,551,838, and U.S. Patent Application Publication No. 2004/0121486, describe devices for the controlled release or exposure of reservoir contents. The devices include a plurality of reservoirs in which contents are isolated until the time selected for release or exposure. For example, the reservoirs can contain a drug formulation for controlled release or sensors for exposure. In several embodiments, each reservoir has a discrete reservoir cap closing off a reservoir opening, and the device includes means for disintegrating or permeabilizing the reservoir cap, for example by electrochemical oxidation or electrothermal ablation.
Reservoir caps generally are self-supporting depending upon the size of the reservoir opening across which they span, i.e., the reservoir opening can be small enough so that the center of the reservoir cap does not require structural support in addition to the support from the substrate edges defining the reservoir opening and the substrate surface surrounding the opening (“streets”) upon which the reservoir caps are secured. However, in many applications—for example to expose a larger sensor area and/or to increase the rate of mass transport of molecules into and/or out of the reservoir—it would be desirable to be able to increase the area of the reservoir opening beyond that which a reservoir cap of certain materials and thickness could support itself. It also would be desirable to provide a device with reservoir caps able to withstand stresses placed upon the reservoir cap in the device's intended application, as certain membranes, while self supporting, nevertheless could be easily torn or fractured by normal application stresses. It would also be desirable to provide, in some instances, a reservoir device having at least one wide, shallow reservoir that can utilize reservoir cap-based techniques for active, controlled reservoir opening.